Split-window and multi-angle methods of sea surface temperature determination: an analysis

A physical model of split-window and multi-angle algorithms for the retriev al of sea surface temperature has been obtained. It is shown that optical t hickness in the thermal infrared window region is approximately represented by a separable function of wavelength and atmospheric variables which grea tly simplify the radiative transfer model. In modelling the temperature ret rieval algorithms we exploit the correlation that exists between the sea su rface temperature and the average temperature of the atmosphere. It is show n that, to the extent this correlation is maintained, there is a simple rel ationship between surface temperature and the brightness temperatures measu red in two split-window or multi-angle channels. The different atmospheric conditions which cause spread in this relationship are briefly discussed. I t is shown that measurements at three optical thicknesses instead of two as in the case of the split-window method improve the SST retrieval accuracy since it can take care of non-equilibrium conditions such as inversions, su rface instabilities, etc., prevailing in the atmosphere.